Problem: $-\dfrac{6}{12} + \dfrac{5}{2} = {?}$
Answer: $ = - {\dfrac{6 \times 1}{12 \times 1}} + {\dfrac{5 \times 6}{2 \times 6}} $ $ = - {\dfrac{6}{12}} + {\dfrac{30}{12}} $ $ = - \dfrac{{6} + {30}}{12} $ $ = \dfrac{24}{12}$